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The great tragedy of science – the slaying of a beautiful hypothesis by an ugly fact.
-Thomas Huxley
Monday, October 3, 2011
I. The Roots of Astronomy A. Archaeoastronomy B. The Astronomy of Greece C. Aristotle and the Nature of Earth D. The Ptolemaic Universe
II. The Copernican Revolution A. Copernicus the Revolutionary
B. De Revolutionibus C. Galileo the Defender D. The Trial of Galileo
III. The Puzzle of Planetary Motion A. Tycho the Observer B. Tycho Brahe's Legacy C. Kepler the Analyst D. Kepler's Three Laws of Planetary Motion E. The Rudolphine Tables
IV. Modern Astronomy
Outline
Monday, October 3, 2011
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Ancient Greek Astronomers
Earth’s shadow is round as seen during an eclipse
Monday, October 3, 2011
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Scale of the Solar System
Size of the Earth + Lunar Eclipse Observations
Size of Moon!!!
Monday, October 3, 2011
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Scale of the Solar System
Size of the Moon + Angular Size in Sky
Distance to Moon!!!
Monday, October 3, 2011
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Scale of the Solar System
Distance to the Moon + Sun/Moon Angle
Distance to Sun!!!
Monday, October 3, 2011
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Scale of the Solar System
Distance to the Sun + Angular Size in Sky
Distance to Sun!!!
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Geocentric Models• Eudoxus (409 – 356 B.C.):
Model of 27 nested spheres
• Aristotle (384 – 322 B.C.),
major authority of philosophy until the late middle ages: Universe can be divided in 2 parts:
Monday, October 3, 2011
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Geocentric Models• Eudoxus (409 – 356 B.C.):
Model of 27 nested spheres
• Aristotle (384 – 322 B.C.),
major authority of philosophy until the late middle ages: Universe can be divided in 2 parts:
1. Imperfect, changeable Earth,
Monday, October 3, 2011
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Geocentric Models• Eudoxus (409 – 356 B.C.):
Model of 27 nested spheres
• Aristotle (384 – 322 B.C.),
major authority of philosophy until the late middle ages: Universe can be divided in 2 parts:
1. Imperfect, changeable Earth,
2. Perfect Heavens (described by spheres)
Monday, October 3, 2011
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The WanderersPlanet: from Greek πλανήτης αστήρ planētēs astēr "wandering star"
Monday, October 3, 2011
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Retrograde (westward) motion of a planet occurs when the Earth passes the planet.
The Wanderers
Motion of the planets across the sky is markedly different than the motion of the stars.
Planet: from Greek πλανήτης αστήρ planētēs astēr "wandering star"
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Refinements to Geocentric Models
Ptolemy’s epicycles(150 AD)
Model survived until Copernican Revolution of 1500’s.
Publication: Syntaxis (the greatest)
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Middle Ages
Islamic Period: 700-1300 AD
• High regard for the science• Religious motives for accurate timekeeping and astronomical observations• Translated Greek texts into arabic• Ptolemy’s Syntaxis (arabic: Almagest)
Contained a catalogue of > 1,000 starsAll were given arabic names
• Measured 23.5 tilt of Earth’s rotational axis with great precision.
Monday, October 3, 2011
Stellar ParallaxWe can judge distances to objects because we observe the world through two vantage points -- two eyes.
Monday, October 3, 2011
Stellar Parallax
Greeks assumed the Earth was not moving because they did not observe parallaxes in the sky.
We can judge distances to objects because we observe the world through two vantage points -- two eyes.
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Parallax angle of the nearest star is less than 1/3600 of one degree.
Ancient astronomers tried to measure parallax via careful naked-eye observations but failed.
Finally detected in 1830 by F. Bessel using telescope.
Stellar Parallax
Monday, October 3, 2011